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Scary.

ie Offline Don Pablo

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Scary.
on: February 19, 2018, 06:37:51 PM
http://www.cree.com/led-components/media/documents/LM80_Results.pdf

I was going cross eyed staring at the Cree LED lifespan datasheets. More specifically the XP-G2 and XP-L sections, because those are in my flashlights. Thinking, wow, that is some wicked performance, while looking at the lifespan numbers at high temps and high currents.

Then I noticed something.
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gb Offline Fuzzbucket

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Re: Scary.
Reply #1 on: February 19, 2018, 06:48:38 PM
... too many words!!!   :twak:

Can you not do me a picture or something?!  :ahhh


00 Offline Mechanickal

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Re: Scary.
Reply #2 on: February 19, 2018, 06:54:47 PM
Lower temp = higher current?
So ambient temp is electrocution power?


no Offline Steinar

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Re: Scary.
Reply #3 on: February 19, 2018, 06:56:25 PM
87 pages of data and you noticed "something"? I'm not surprised, really, but it would have been sort of nice if you shared what you noticed...


cy Offline dks

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Re: Scary.
Reply #4 on: February 19, 2018, 06:59:12 PM
obviously the shock Pabloed his mind and he is currently unable to post...    :D :D :D :D
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ie Offline Don Pablo

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Re: Scary.
Reply #5 on: February 19, 2018, 06:59:54 PM
Hold your horses, I'm typing a reply and building hype.  :D
Hooked, like everyone else. ;)

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gb Offline Fuzzbucket

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Re: Scary.
Reply #6 on: February 19, 2018, 07:13:32 PM
... too many words!... too many words!...  :ahhh :ahhh :ahhh


ie Offline Don Pablo

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Re: Scary.
Reply #7 on: February 19, 2018, 07:37:41 PM
Ok, thats dinner finished. :whistle:
What was I typing? Oh yeah....

Keep in mind that unless they are abused, LEDs don't "fail" like incandescent light bulbs, they slowly dim as they age. And that in these sort of tests, you MAY NOT officially estimate the rate of dimming beyond a certain period of time, which is determined by how long the test ran.

There are several tests in the XP-G2 section that ran for nearly 14k hours.

One was done at an ambient temperature of 85 °C (185 °F) with a current of 500 mA. At that current, an XP-G2 will give you probably over 250 lumens (I didn't do any math, okay?!.  :D).
A decent max brightness for most AA lights, and most AAA lights go nowhere near that.
Presumably the LED itself was at an even higher temp.  :ahhh
Based on the results of that test, which they ran for 14,000 hours on a sample of 20 LEDs, they listed the projected lifespan until the LEDs dimmed to 70% of their original performance as  > 81,600 hrs.

What does that mean? It means that the LEDs were degrading in performance so slowly, that even after a 14k hour test, the testing standards won't allow them to give an estimation of when the performance would reach 70%.  ::) :ahhh All they were allowed to say was that it was over 81,600 hrs.  :o

Even scarier, is that it is the same story with performance degradation to 90%. The rate of degradation is so slow in these conditions, that they can only say: > 81,600 hrs.  :facepalm:


Summary:
If room temperature is 85 °C, which will make your LED degrade faster than a 25 °C room temperature, and the output is around 250 lumens, and it has good heatsinking, and you use it 4 hours a day, your flashlight LED will take at least 50 years* to degrade to 90%, outliving a good few circuit board replacements in that time.  :ahhh


*Not accounting for air and moisture and sunlight related degradation obviously.
« Last Edit: February 19, 2018, 07:41:39 PM by Pablo O'Brien »
Hooked, like everyone else. ;)

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nz Offline Syncop8r

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Re: Scary.
Reply #8 on: February 19, 2018, 07:42:59 PM
Summary:
If room temperature is 85 °C, which will make your LED degrade faster than a 25 °C room temperature, and the output is around 250 lumens, and it has good heatsinking, and you use it 4 hours a day, your flashlight LED will take at least 50 years to degrade to 90%, outliving a good few circuit board replacements in that time.  :ahhh
So, given that Hell is for eternity, how many LEDs will I need?  :think:


ie Offline Don Pablo

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Re: Scary.
Reply #9 on: February 19, 2018, 07:47:13 PM
And it is the same story with another (shorter) test, run at 105°C ambient temp(WHERE DO THEY THINK YOU'D BE USING THESE LEDS?! :rofl:) with 1000 mA current. 1000 mA in an xp-g2 will give you 500 lumens probably.
 > 51,400 hrs for 90%, 80% and 70%, the "only"  51,400 hrs is because they ran the test for only 8,600 hours.
Hooked, like everyone else. ;)

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00 Offline Mechanickal

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Re: Scary.
Reply #10 on: February 19, 2018, 07:47:41 PM
I just figured that a LED outlives the electronics behind them. Unless it gets fried because of an error like on an outside light here... smurfy cheap junk...

So... nothing new I guess...

All the fuzz for nothing ::)


cy Offline dks

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Re: Scary.
Reply #11 on: February 19, 2018, 07:48:06 PM
usually the boards get damaged first but  you will also see damage to the LED after a drop, or because of humidity. I have replaced several lamps (for various reasons) and have seen about 4 CREE torches fail because of damage to the LED
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cy Offline dks

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Re: Scary.
Reply #12 on: February 19, 2018, 07:49:27 PM
note - direct drive the LED to see if it is damaged, 3V
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ie Offline Don Pablo

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Re: Scary.
Reply #13 on: February 19, 2018, 07:55:05 PM
note - direct drive the LED to see if it is damaged, 3V
People regularly direct drive LEDs with 4.2v lion batteries.
Hooked, like everyone else. ;)

All hail the hook!


ie Offline Don Pablo

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Re: Scary.
Reply #14 on: February 19, 2018, 07:57:25 PM
usually the boards get damaged first but  you will also see damage to the LED after a drop, or because of humidity. I have replaced several lamps (for various reasons) and have seen about 4 CREE torches fail because of damage to the LED
The board is what I’m worried about on my Ti3. I think that it is the main obstacle in the way of it living as long as a SAK.  :cry:
Hooked, like everyone else. ;)

All hail the hook!


cy Offline dks

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Re: Scary.
Reply #15 on: February 19, 2018, 07:59:22 PM
note - direct drive the LED to see if it is damaged, 3V
People regularly direct drive LEDs with 4.2v lion batteries.
I know - this was just a suggestion for an easy test  to see if the LED is damaged   use 2AAs for example
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ie Offline Don Pablo

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Re: Scary.
Reply #16 on: February 19, 2018, 08:01:01 PM
note - direct drive the LED to see if it is damaged, 3V
People regularly direct drive LEDs with 4.2v lion batteries.
I know - this was just a suggestion for an easy test  to see if the LED is damaged   use 2AAs for example
Oh, it’s a testing method.  :facepalm:
I misunderstood  what you meant.  :oops:

I just figured that a LED outlives the electronics behind them. Unless it gets fried because of an error like on an outside light here... smurfy cheap junk...

So... nothing new I guess...

All the fuzz for nothing ::)
It inspires you to try and use better quality electronics, doesn’t it? :dd:

If only they hadn’t discontinued lead solder for consumer products..  :think:
Hooked, like everyone else. ;)

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nz Offline Syncop8r

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Re: Scary.
Reply #17 on: February 19, 2018, 08:01:23 PM
And it is the same story with another (shorter) test, run at 105°C ambient temp(WHERE DO THEY THINK YOU'D BE USING THESE LEDS?! :rofl:)
Hell of course.
See you there.  :drink:


ie Offline Don Pablo

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Re: Scary.
Reply #18 on: February 20, 2018, 12:15:06 PM
And it is the same story with another (shorter) test, run at 105°C ambient temp(WHERE DO THEY THINK YOU'D BE USING THESE LEDS?! :rofl:)
Hell of course.
See you there.  :drink:
Lemme see....
Eternity is the same as infinity, is it?
If you are spending an infinite amount of time somewhere, and you need a supply of flashlights....
Because of the nature of infinity, if each flashlight has a lifespan of anything less than infinity, no matter how large a lifespan it is, you will need an infinite amount of flashlights to last you through eternity in Hell.
I think thats how infinity works. :think:
You better hope that you brought your edc bag, the one thats infinitely bigger on the inside.  :facepalm:
« Last Edit: February 20, 2018, 12:16:08 PM by Pablo O'Brien »
Hooked, like everyone else. ;)

All hail the hook!


us Offline Blackbeard

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Re: Scary.
Reply #19 on: February 21, 2018, 01:59:00 AM
I think the oldest light I have is my olight t15 gotta be like 10+ years old and still going strong, these emitters last quite a long time


us Offline Higgins617

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Re: Scary.
Reply #20 on: February 21, 2018, 02:35:24 AM
And it is the same story with another (shorter) test, run at 105°C ambient temp(WHERE DO THEY THINK YOU'D BE USING THESE LEDS?! :rofl:)
Hell of course.
See you there.  :drink:

Firefighters use pretty nice LED lights now, maybe that's partially the reason? Or they said Smurf we can't say they have an indefinite span, let's kill one.
I'm a total legend..... in my own mind- Herley


 

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